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我创建了一个读取wordcount示例[1]的映射输出的映射方法。此示例远离使用MapReduce提供的IdentityMapper.class
,但这是我发现为Wordcount创建工作IdentityMapper
的唯一方法。唯一的问题是这个Mapper花费的时间比我想要的要多得多。我开始认为,也许我正在做一些冗余的东西。任何帮助来提高我的WordCountIdentityMapper
代码?改善Wordcount中的身份映射器
[1]身份映射器
public class WordCountIdentityMapper extends MyMapper<LongWritable, Text, Text, IntWritable> {
private Text word = new Text();
public void map(LongWritable key, Text value, Context context
) throws IOException, InterruptedException {
StringTokenizer itr = new StringTokenizer(value.toString());
word.set(itr.nextToken());
Integer val = Integer.valueOf(itr.nextToken());
context.write(word, new IntWritable(val));
}
public void run(Context context) throws IOException, InterruptedException {
while (context.nextKeyValue()) {
map(context.getCurrentKey(), context.getCurrentValue(), context);
}
}
}
生成该mapoutput
public static class MyMap extends Mapper<LongWritable, Text, Text, IntWritable> {
private final static IntWritable one = new IntWritable(1);
private Text word = new Text();
public void map(LongWritable key, Text value, Context context
) throws IOException, InterruptedException {
StringTokenizer itr = new StringTokenizer(value.toString());
while (itr.hasMoreTokens()) {
word.set(itr.nextToken());
context.write(word, one);
}
}
public void run(Context context) throws IOException, InterruptedException {
try {
while (context.nextKeyValue()) {
map(context.getCurrentKey(), context.getCurrentValue(), context);
}
} finally {
cleanup(context);
}
}
}
由于
[2] Map类,